Radian Crewed SSO Spaceplane

[ncb1397]

Was there some material science breakthrough?

ermm, not exactly new, but composites that can handle cryogenics(i.e. rocket lab electron)?

In the past, using composites for the storage of cryogenic liquid fuel – liquid hydrogen, liquid oxygen, liquid methane – has been met with concern revolving around the potential for leaks, due to microcracking of traditional carbon/epoxy composite laminates at extremely low temperatures. A leap forward with the technology seems to be underway.

https://www.compositesworld.com/articles/composite-pressure-vessels-take-on-cryogenic-temperatures

I mean, the ITS presentation that people took seriously suggested that the tanker would have a dry mass of 90 t, a propellant mass of 2500 t and an ISP of 361 at sea level and 382 in vacuum. Delta v would be 11.5 - 12.5 km/s which would easily be enough for SSTO (and then some).

[john smith 19]

I've heard that about pintles before, but never from someone who worked on one (they tend to laugh at that). Face-shutoff is also annoying to get working from what I've heard, but I think Gary has done it before so he may have a head start.

I don't think the pintle has ever had a decent chapter in a design text book devoted to it.

Film cooling is the strangest choice to me. Armadillo did a similar cooling method, and the Isp hit was large.

Another odd choice.   
I know people have their habits and preferences but anything close to SSTO is so demanding (especially if you're going with a straight rocket engine) you have to re-consider everything. We know that only winged stages have been recovered from orbit intact (everything else has basically been a payload on ascent).  Beyond that everything has to be up for trading to get to a minimum product (or in this case a demonstrable stage of development that can unlock the next round of funding).

I keep hoping for Doug Jones (Ex Rotary Rocket and XCOR) to write an engines book but I guess it's never going to happen. 

The mention of an advanced carbon fiber LOx tank may suggest linerless to reduce weight?

Rotary may have been the first in the industry to try that and make it work.

There are 2 issues with composites.

1) Once you get away from straight shapes of revolution complexity rises fast.   This is a plane.

2) SSTO (even assisted SSTO) requires you look at the total design problem under all conditions.  Rotary were among the first (the first?) to get composite LOX tanks (and LOX chamber cooling) working.

But then you've got to get that structure back  and now the problem isn't what's inside the tank, it's what's outside.

With SSTO you can't stage your problem away when things get tough. They have to be considered from day one. In fact you would probably do as well to work backward and ask  yourself "OK So our customers say they want a payload of X x Y x Z meters and M Kg to this orbit (or N passengers).  What do have to wrap that in to get it there (and keep it there for N hours) ? Now what do have to wrap the wrapping (propellant, engines and structure) in to get that back?"

Materials wise stainless steel still looks very interesting. It blunts so many of the problems in terms of formability, thermal conductivity, high and low temperature capability. 
Stainless steel. The "half way" material to get you halfway to anywhere.   

[libra]

Very crude calculations...

9.81*362*ln((200+4.5)/(11+4.5)) = 9161 m/s

Let's suppose their rocket plane weights 200 mt (completely arbitrary number, but one has to start to speculate somewhere !)

Payload is 4.5 mt : 10 000 pounds.

Specific impulse: I retained the RD-0124 vacuum and record, since they have nozzles adapted to sea level conditions (otherwise, would have been 340 seconds at sea level for kerolox)

From there it is pretty simple: the empty weight must be 11 mt. If they bust that limit : the thing won't go into orbit anymore !

Thus, propellant mass fraction... 200-(200*0.945) = 11 so 0.945

Now, the all time record I already mentioned remains with Titan II stage 1 at 0.962 : 117 mt full, 4.45 mt empty (from memory)

Except that Titan II stage 1 was just an expendable rocket stage. An aluminium cylinder with LR-87 at the bottom, and that was it.

So basically, they have to wrap a rocketplane around a rocket stage -and stay within their necessary mass fraction limit 0.945. Which is already extremely close from the all time record of 0.962... which hadn't any rocketplane around its rocket stage.

Mind you, I did such calculations for my suborbital refueling pet peeve. It amounts to wrapping Mitch burnside Clapp Black Horse / Black Colt "rocketplane elements" around the said Titan II stage 1.

End result: even that barebone hybrid instantly ruins the propellant mass fraction well below 0.90, 0.85 best case. And it can't go into orbit - no way.

---------------------------

Now, if they switched to TAN - Thrust Augmented Nozzle, presently buried at / by Aerojet - it COULD be made to work.

They need Melvin Bulman !

"Variable Element Launcher" - see attached. THIS is the way to go, to get a workable SSTO. No need for a rocket sled.
Best of kerolox and hydrolox, altogether - high density and specific impulse.

Through Aerojet, Bulman is kind of "heir" of Beichel and Salkeld extensive tripropellant research started in 1970. He has carried on and gone a step further with TAN, the true accomplishment of tripropellant rocketry.

----

Alternative 1 : put an expendable stage and stick with suborbital. Note that inflatable heatshields could make expendable upper stages reusables.

Second alternative: build two of these things and try suborbital refueling :p 

[Davidthefat]

If you want to see a legacy example of a face shut off pintle injector used in the LMDE. The fuel annulus isn’t shown, but is on the outside of the moveable sleeve.

This isn’t the only way to do a face shut off on a pintle, but is just one instance of it.

Just curious on how they plan on actually sealing on shutoff in their design shown in the patent. Especially on the annulus side with no apparent way to seal.

[Eerie]

TBH: this looks like someone drew a "cool spaceplane" without considering feasibility at all. It's something I used to "invent" at the age of ten.

[ncb1397]

Very crude calculations...

9.81*362*ln((200+4.5)/(11+4.5)) = 9161 m/s

Let's suppose their rocket plane weights 200 mt (completely arbitrary number, but one has to start to speculate somewhere !)

Payload is 4.5 mt : 10 000 pounds.

Specific impulse: I retained the RD-0124 vacuum and record, since they have nozzles adapted to sea level conditions (otherwise, would have been 340 seconds at sea level for kerolox)

From there it is pretty simple: the empty weight must be 11 mt. If they bust that limit : the thing won't go into orbit anymore !

But what is the staging velocity for the rocket sled? I believe that the land based manned speed record is subsonic but unmanned rocket sleds have reached up to mach 8. It probably doesn't make sense to make a manned version from the start.

[Eerie]

But what is the staging velocity for the rocket sled? I believe that the land based manned speed record is subsonic but unmanned rocket sleds have reached up to mach 8. It probably doesn't make sense to make a manned version from the start.

Mach 8 parallel to the ground at sea level is not helpful.

[john smith 19]

But what is the staging velocity for the rocket sled? I believe that the land based manned speed record is subsonic but unmanned rocket sleds have reached up to mach 8. It probably doesn't make sense to make a manned version from the start.

Good question. 

But you're wrong about the land speed record. As of 1997 Thrust SSC reached 763.035mph, or M1.016 at sea level.

That said transonic drag around M0.9-1.1 is going to be severe at ground level.

Requiring the design be crewed from the start (like the Shuttle, but unlike every other crewed space vehicle) would be a majorhandicap in development, and is simply unnecessary (unless you have a NASA center that demands  the design needs to be crewed from the start    )

[Asteroza]

But what is the staging velocity for the rocket sled? I believe that the land based manned speed record is subsonic but unmanned rocket sleds have reached up to mach 8. It probably doesn't make sense to make a manned version from the start.

Good question. 

But you're wrong about the land speed record. As of 1997 Thrust SSC reached 763.035mph, or M1.016 at sea level.

That said transonic drag around M0.9-1.1 is going to be severe at ground level.

Requiring the design be crewed from the start (like the Shuttle, but unlike every other crewed space vehicle) would be a majorhandicap in development, and is simply unnecessary (unless you have a NASA center that demands  the design needs to be crewed from the start    )

Didn't the air force send guys in manned rocket sleds going faster than sound, ostensibly for ejection tests? Or did that only involved animals...

[Robotbeat]

300mph is all the sled goes up to. That's a very good number, IMHO. Any higher than that and airframe stresses increase, and you start getting local supersonic flow. And to go 600mph, you'd need to quadruple your track length (for the same acceleration).

[john smith 19]

300mph is all the sled goes up to. That's a very good number, IMHO. Any higher than that and airframe stresses increase, and you start getting local supersonic flow. And to go 600mph, you'd need to quadruple your track length (for the same acceleration).

Raising the sled speed is attractive. It brakes harder but all that mass should be in the sled, which is not an issue and every m/s you raise the vehicle speed (at full GTOM) is a win.

The joker is a launch abort with the sled at maximum speed just about to separate the vehicle. RASV did it by metal plates digging into the ground and IIRC parachutes for extreme emergency. Water cooled brakes are an option as well. 

Obviously a lot of that GTOM is LOX.  If you could safely vent a lot of that then the mass you have to decelerate drops a lot. Sadly a LOX cooled emergency braking systems is a complete non starter. 

[libra]

Yes the land speed record (absolute, unmanned, all vehicles) is some kind of rocket sled, circa mach 8.

https://en.wikipedia.org/wiki/Rocket_sled

Mach 8.5 - but I'm not sure it is applicable to throwing a rocketplane !

[Eerie]

They should partner with Spinlaunch.

[ncb1397]

Probably the closest thing to this system (at least for the first phase of launch) was "snark" intercontinental cruise missile testing that was done on a rocket sled prior to the rockets being available.



I guess if the spaceplane doesn't quite make orbit as a single stage, you could use relatively small rockets similar to how the snark was launched normally for that extra kick to close the performance requirements (the closer to SSTO you get, the smaller and cheaper SRBs you can use). That makes it seem rather space shuttle like (but also quite different given the integrated fuel tank and the SRBs potentially being much much smaller).

[libra]

I hate to be a nitpicker, but Snark was a cruise missile... no ballistic trajectories for them.

[john smith 19]

Yes the land speed record (absolute, unmanned, all vehicles) is some kind of rocket sled, circa mach 8.

https://en.wikipedia.org/wiki/Rocket_sled

Mach 8.5 - but I'm not sure it is applicable to throwing a rocketplane !

Indeed.

Track, sled and air launch have certain things in common. They add complexity but can lower launch vehicle mass and can add launch site flexibility.

In some ways sled launch is a good compromise. Not as fixed as needing a track so you can launch in any direction (that's a good thing) and provided you're running over bedrock you can make the sled almost as big as you like (if you can find jet or rocket engines big enough), whereas launch aircraft size is a major constraint for air launch.

However the number of groups that have experience of breaking the sound barrier at ground level is very limited (ejector seat mfgs and Sandia with the USAF come to mind).  Without LH2 this thing is so marginal you need every edge you can get so faster is better but >M1 at ground level raises serious safety issues

Staying with kerosene when you're already OK with LOX still baffles me, unless you want to retain wing tanks, which you might well want to minimize surface area to protect on reentry.

And then there is the CoG/CoM shift that happens as your vehicle operates over 23 Mach numbers and 60+Km of altitude through the sensible atmosphere....

With engines at the back their control surfaces are going to be quite busy.   

[john smith 19]

It's easier to get higher mass ratios with denser propellants, at least this has a better chance of happening than any hydrogen SSTO.

That depends on what you're doing with the hydrogen.

I wish them luck and I'll look forward to seeing what funding they have attracted and what progress they've made in say 5 years time.

2025 should be an exciting year.

[edzieba]

In some ways sled launch is a good compromise. Not as fixed as needing a track so you can launch in any direction (that's a good thing) and provided you're running over bedrock you can make the sled almost as big as you like (if you can find jet or rocket engines big enough), whereas launch aircraft size is a major constraint for air launch.

All of the hypersonic (and for that matter supersonic) sleds have been on tracks. The only reason they're 'sleds' on 'tracks' and not on 'rails' is because they slide on bearing surfaces rather than roll on wheels.

[Asteroza]

In some ways sled launch is a good compromise. Not as fixed as needing a track so you can launch in any direction (that's a good thing) and provided you're running over bedrock you can make the sled almost as big as you like (if you can find jet or rocket engines big enough), whereas launch aircraft size is a major constraint for air launch.

All of the hypersonic (and for that matter supersonic) sleds have been on tracks. The only reason they're 'sleds' on 'tracks' and not on 'rails' is because they slide on bearing surfaces rather than roll on wheels.

Has anyone every actually built a high speed unfixed "floating" sled before? Something that can run on salt flats or lakebeds? Say a hovercraft, or a ground effect PAR-WIG? Some old concept designs for an SSTO had a "flying" jet sled/platform that resembled a WIG.

[HMXHMX]

I can make this one comment and no other.  I (and my colleague Bevin McKinney) have our names on the patents because of our past contractor role with Radian.  He and I make our living as contractors/consultants.  We are not currently engaged by Radian, but we remain under NDA so can’t participate in this sub-forum.